A wirebond semiconductor package comprises an integrated circuit (“IC”) electrically coupled to a package substrate using bond wires. In turn, the package substrate is electrically coupled to a circuit board using solder balls. In this way, multiple electrical connections are established between the integrated circuit and the circuit board. An IC in a wirebond package may require access to one or more voltage levels. For example, the IC may require access to voltage sources of 1.1 V, 3.3 V, and 5 V, in addition to a ground connection.
To this end, wirebond package substrates comprise multiple metal planes (i.e., layers). Each of these metal planes may carry a different voltage level. For example, one metal plane may carry a 3.3 V potential and another may carry a 0.0 V (i.e., ground) potential. Each of these metal planes may be electrically coupled to metal rings abutting (e.g., metallized on) the package substrate and surrounding the IC, called a power ring. Each power ring makes accessible to the IC a voltage potential found on a metal plane coupled to that power ring. For example, the IC may access a 5 V source by way of a power ring that is electrically coupled to a 5 V metal plane.
The IC accesses the power rings using fine-pitch bond wires. However, because these fine-pitch bond wires are substantially narrow and long, the bond wires carry a considerably high inductance that may compromise signal integrity. Also, in wirebond packages that do not support multiple planes in the substrate, substantially long, narrow metal traces may be used to carry electrical signals from solder balls to the power rings. Such long, narrow metal traces also carry substantial levels of inductance that may negatively impact signal quality. Finally, the power delivery to the core of the die requires long traces from bond pads generally arranged on the die periphery to the core regions of the die. These traces cause voltage (IR) drops and loss of signal integrity.